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Alpha
(@alpha)
Estimable Member
Clicking X axis belt wheel

Hi folks,

Had a blob of doom recently, so just replacing the hotend, however have also noticed an odd clicking that's causing the X axis calibration to fail.

I've attached a video, it's like the belt pulley isn't attached fully which is strange. Not sure what's the easiest way to get access to this as is stuck behind the vertical screw rods and the  zaxis plate.

Can anyone help diagnose? Is there a dodgy bearing or something? 

Many thanks in advance!

 

 

Posted : 10/08/2019 9:59 am
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

https://vimeo.com/353084319

Link to video above - you can see the 'click' at the end, it's like it's not spinning freely....
This post was modified 2 years ago 3 times by Alpha
Posted : 10/08/2019 10:07 am
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(@)
Illustrious Member
RE: Clicking X axis belt wheel

There supposed to be a screw that goes through the bracket front to back and through the pulley.  Looks like the nut came off ...  

Step 5:

https://manual.prusa3d.com/Guide/3.+X-axis+assembly/508?lang=en

 

This post was modified 2 years ago by --
Posted : 10/08/2019 10:52 am
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Yes, the nut is still there, but assume it's come loose enough for the bolt to escape or something?  

There doesn't happen to be some micro Allen key or something that'll save me pulling the whole thing apart to tighten the nut and bolt?  

Posted : 10/08/2019 11:57 am
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Hmm.

This might save me an hour or two...?

Posted : 10/08/2019 12:12 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Ok, have opened up and think the X axis toothless bearing needs replaced.

I've hunted around and struggled to find - I think this is because Prusa aren't using the standard name in their instructions or they refer to it as a '623h bearing with housing'.

I think it is generally referred to as an idler pulley, but I cant pin down which size it is, ie

https://e3d-online.com/gates-powergripr-smooth-idler-12mm

https://e3d-online.com/gates-powergripr-smooth-idler-9mm

https://e3d-online.com/gates-powergripr-smooth-idler-6mm

Can anyone help give me the correct name and good brands to replace?

Posted : 10/08/2019 3:50 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Ps, here's a shot of the problem bearing....! 

 

Attachment removed
Posted : 10/08/2019 4:28 pm
JoanTabb
(@joantabb)
Moderator
RE: Clicking X axis belt wheel

Hi Katie,

those three idlers are all wrong, they have 5mm bores, where as the prusa uses a 3mm bore idler.

these are probably more like what you are looking for

https://www.ebay.co.uk/itm/UK-STOCK-2pcs-Prusa-I3-mk3-mk2-mk2s-x-y-aluminum-Flat-Idler-bearing-623h/401676171997?hash=item5d85c3fadd:g:9ZkAAOSwya1cXXsu

looking at the roller it appears to be a twin bearing alternative. which may well perform better than the original

where are you located?

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 10/08/2019 6:19 pm
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(@)
Illustrious Member
RE: Clicking X axis belt wheel

The idler pulley is 6mm width, 2mm pitch, abt. 20 tooth equiv, 3mm bore.  Except the pitch is meaningless since it is a smooth pulley. 

Here's a source: you could buy the 20 toothed version and consider it an upgrade rather than a repair. lol. And you get parts for X and Y in one shot.  Why an upgrade? Some are saying the teeth on the belt cause sub-step artifacts when spinning around a smooth pulley.  Personally I'm on the fence... but with this seller you have options.  Just be sure you click the 6mm wide, 3mm bore.

https://www.amazon.com/WINSINN-Aluminum-Timing-Pulley-Printer/dp/B07MW36HKG

ps: and when you install the new pulleys, add a drop of machine oil on the inner race of the bearings.

This post was modified 2 years ago by --
Posted : 10/08/2019 6:50 pm
bobstro liked
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(@)
Illustrious Member
RE: Clicking X axis belt wheel

And one last thought: 

Loosen the X-Axis belt by relieving all the pressure on the adjustment screw near the X-motor. Or take off the drive gear. It will make installing the new pulley a lot easier.

You can then raise the Z-Axis to the top, support the extruder with a couple of boxes, pull the top Z-Axis supports, remove the T-Nut screws so they are free,  then spin the T-nuts off by hand and then you can lift the Z as need to access the idler hardware.  Pretty easy to do and no major tear down required.

Reassemble with sliding the Z-Axis back down carefully aligning the bearings, rest it on the boxes, hand thread the T-Nuts back onto the lead screws, attach them to the axis parts (try to get the as even/level as you can); reattach the top end stop brackets. Put the belt drive gear back on (you might have to work at it a bit, but it is doable).  Be sure to use FLAT FIRST when tightening the gear set screws: do NOT tighten the second screw until after the set screw on the flat is tight.  Retension the belt to whatever it was before you started.

Once it's all back together, turn on the printer, move the Z-Axis until it is hammering the top stops and hitting both sides.  You should be good to go.

 

This post was modified 2 years ago by --
Posted : 10/08/2019 7:02 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Tim, Joan - before I respond, if I can just take a moment to say you both rock. Read countless other posts for others that you've made and can't begin to describe how valuable your knowledge and expertise has been. Know it's one of the strange effects of the digital age, that Joan and Tim can be household names for thousands of people, yet you're unaware, so thought I would point it out. Your patience and detail of response has been invaluable for me even indirectly in getting up to speed with a new technology...

Anyhoo 

Joan: Edinburgh,UK (well the latter part is until Boris/Nicola have their way in wrecking things... 😉 ). Really useful link - I'm always a bit concerned about an 'ebay part' - is this irrational?

Tim: Great advice, loads in there so will digest. I'd read some similar posts about teeth Vs smooth and agree I'd ended up on the fence ( or more precisely I'd ended up 'if I don't know for sure it'll improve, then do mess with it'). Interesting to hear your thoughts.

Great tips on disassembly - that'll save me overdoing things. I'm thinking I might use this as an opportunity/excise to upgrade to the mk3s anyway, so that'll let me feel it's more productive.... 😉

And sorry for the stupid questions, but when you say add a drop of machine oil to the racing - what is the racing and what's the best machine oil? I've got a whole range of lithium wd40, countless others, but would want to pick the right one....!

 

This post was modified 2 years ago by Alpha
Posted : 10/08/2019 7:52 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Ps Joan  - how can you tell that they're twin bearings from the link you sent - be good to know what I should look out for!

Posted : 10/08/2019 9:01 pm
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(@)
Illustrious Member
RE: Clicking X axis belt wheel

Races are what the bearings roll on ... easier to get oil on than the bearings themselves.  The idler bearings are small enough getting grease inside then is probably more trouble than it's worth.  But the 'best' would be to use a spray lithium grease and try to wet the inner bearings, then wipe the excess off before installing.  A drop of oil (like sewing machine oil) will suffice.  WD40 is NOT a good lubricant - it's actually designed to displace moisture (Water Displacement oil formula 40 -- what is really odd is I knew that trivia without Googling -- I need a better life). 

Posted : 10/08/2019 9:12 pm
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(@)
Illustrious Member
RE: Clicking X axis belt wheel

These really aren't double bearings ...

https://us.misumi-ec.com/vona2/detail/221000528965/?HissuCode=623H

This post was modified 2 years ago by --
Posted : 10/08/2019 9:29 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Clicking X axis belt wheel

Hi Tim - really useful thanks, know exactly what to aim for now!

Just to be clear re wd40, I've got a range of their lubricants (which they perhaps confusingly sell under their wd40 brand).

So would their lithium grease spray be ok - eg:

Example link

 

Posted : 11/08/2019 6:34 am
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(@)
Illustrious Member
RE: Clicking X axis belt wheel

Spray Lithium Grease is good stuff ... just a bit messy when spraying.  But you must shake very well between squirts or all you get is solvents, one or two shots of grease into the crevasses around the retainer should do it, wipe off any over spray, and will last until the next tear down.  Bearings will be as quiet as is possible.    Can also be squirted on to a paper towel and wiped on the rods to help keep the linear axis bearings from drying out.

 

Another option is 3-in-1 Oil: 3 oz. Multi-Purpose Precision Lubricant Liquid Oil - a drop or two (not more) on the belt idler bearings ... will last until the next tear down, a bit noisier than grease.  Not recommended for the linear axis bearings, but a drop or two on the rods is better than nothing if the bearings were installed without grease.  Even 20w engine oil is better than nothing.

Posted : 11/08/2019 7:47 am
Justin Porteus
(@justin-porteus)
Active Member
RE: Clicking X axis belt wheel
Posted by: @-2

The idler pulley is 6mm width, 2mm pitch, abt. 20 tooth equiv, 3mm bore.  Except the pitch is meaningless since it is a smooth pulley. 

Here's a source: you could buy the 20 toothed version and consider it an upgrade rather than a repair. lol. And you get parts for X and Y in one shot.  Why an upgrade? Some are saying the teeth on the belt cause sub-step artifacts when spinning around a smooth pulley.  Personally I'm on the fence... but with this seller you have options.  Just be sure you click the 6mm wide, 3mm bore.

https://www.amazon.com/WINSINN-Aluminum-Timing-Pulley-Printer/dp/B07MW36HKG

ps: and when you install the new pulleys, add a drop of machine oil on the inner race of the bearings.

Amazon link is dead.  Found this one:

https://amzn.to/39nXRJZ

Seems to fit the specs (6mm wide, 3mm bore).

I just had this same problem with my Y axis pulley, and found this thread to be very helpful.  Hopefully I have made it at least slightly more helpful 😂

Posted : 28/11/2020 4:58 pm
JoanTabb
(@joantabb)
Moderator
RE: Clicking X axis belt wheel

@katie-o

Hi Katie, 
May I politely protest about misrepresentation...    I live in Halifax not Edinburgh. Lol!

Ebay is not the peak of engineering prowess, however, when My X axis idler pulley failed on my Mk1 Prusa Printer I bought a replacement ball race  from the local bearing specialist, and fitted it to the aluminium roller provided by Prusa,  It failed a second time... 

I replaced the roller with a twin bearing toothed wheel roller from  a lesser quality source.... 
that printer is still working, it is now a Mk2 and is still using the same roller. 

I have four Original Prusa FDM printers and a Wannabe Prusa (Geeetech Prusa i3 ProB) which all wear twin bearing idlers on both the X and Y axis 

I am no expert,  but I believe in the possibility that the single bearing in the Prusa roller may on occasion move off center and become stressed enough to dissassemble it's self...  mine certainly wasn't tight in the roller body. 

No I have to admit that I am a bit self centred and decided to step away from the Prusa Roller, and go for a more ballanced approach... 

the rollers I mentioned have two seperate ball races, one each side.   I have to admit I have never actually looked, but it is likely the bearings are pressed in to the roller body and fill the space between the sides, thus keeping them in position and balanced. 

So far, (Fingers crossed) I have never had to replace a twin roller idler. 

the Idler rotates between two plastic faces on a stainless steel screw. it is unproven but probable that a little additional lubrication will make the roller rotate more smoothly

I agree that the WD40  situation is confusing...  

WD40 White Lithium, grease should be an adequate lubricant for the cheeks of the roller. 

I prefer the toothed Roller, rather than the smooth roller, again, it's not proven, but I believe the smooth roller, pressing against the teeth on the GT2 / 2GT belt, is likely to deform the teeth and cause the belt to loosen with use... , 

so all in all, I actually have no good reason, or proof to offer apart from Five working printers...  

these rollers are not particularly expensive  so perhaps you could try them, and maybe even press the faulty bearing out of the Prusa roller and order a replacement for that too, and if your twin bearing idler rollers ever break,  you will have the repaired idler to replace it immediately... 
🙂

the link Justin points to also mentions Double, Motor grade bearings, and although Justin has highlighted the smooth version, the same vendor also provides toothed versions. 

I wish you all the best which ever option you take. 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 28/11/2020 8:58 pm
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